The present invention is directed to power distribution networks for integrated circuits. More particularly, the present invention is directed to reducing impedance of power distribution networks.
Power distribution networks are a typical manner in which to provide power to packaged integrated circuits. The power distribution network includes a power supply that generates an appropriate voltages employed to bias the integrated circuit and any other circuits included therewith in a common package.
During normal operations of the integrated circuit, the power usage of the same fluctuates. The power fluctuation varies, inter alia, the impedance of the integrated circuit, which may interfere with operation of the integrated circuit resulting in faulty operation of the same. As a result, there have been several attempts at controlling the impedance of integrated circuit systems.
An existing technique employs multiple low-inductance bypass, or decoupling capacitors. Decoupling capacitors provide a momentary charge to compensate when active devices change current consumption. This momentarily stabilizes the current fluctuation caused by the changing current consumption of the integrated circuit, thereby attenuating impedance fluctuations caused by the varying current consumption. The charge in the bypass capacitors is replenished from the power supply that is connected between each power plane and ground. Usually several hundreds of decoupling capacitors are included in a typical integrated circuit package to attenuate switching noise. However, the presence of decoupling capacitors cause resonance in the power distribution that presents as increased impedance of the same. The resonance is a naturally occurring parasitic phenomena, e.g., inductance, resistance, capacitance, present in the integrated circuit, the package, and power distribution network results in resonance when subject to a time varying current.
Thus, there is a need for to reduce the impedance presented by a power distribution network used to bias an integrated circuit.